The toxicity problems arising when foreign matter is introduced into higher eukaryotic cells, especially with transfection with DNA, are obviated by expression in the cell of gene products that block the apoptosis induced by the transfection process and/or by treating the cells with anti-inflammatory substances. Preferred anti-apoptosis genes are Bcl-2, E1B 19K or an anti-apoptotic gene of the CELO avian adenovirus; used as preferred anti-inflammatory substance in the adenovirus VA1, which is introduced into the cell in the form of VA1 DNA. These measures help to achieve a long-lasting gene expression.